Reservoir characteristics and genetic differences between the second and fourth members of Sinian Dengying Formation in northern Sichuan Basin and its surrounding areas

Yong LI,Xingzhi WANG,Mingyou FENG,Deming ZENG,Shengyang XIE,Rui FAN,Liangjun WANG,Tao ZENG,Xuefei YANG

Fig. 3. Major types of reservoir rocks and pore space in the ROI. (a) Gucheng section, Wangcang, Deng-2 Member, thrombolitic dolostone, inter-algal frame pores completely filled with multi-phase dolosparite, polarized light; (b) Gucheng section, Wangcang, Deng-2 Member, stromatolitic dolostone, intra-laminal dissolved pores partially filled with multi-phase dolomite, polarized light; (c) Shuimo section, Wangcang, Deng-2 Member, thrombolitic dolostone, inter-algal frame dissolved cavities partially filled with dolomite, poor connectivity; (d) Yangba section, Nanjiang, Deng-2 Member, dolomitic karst breccia, residual cavities in grape lace-shaped cement; (e) Hujiaba section, Ningqiang, Deng-4 Member, thrombolitic dolostone, inter-algal frame pores partially filled with bitumen; (f) Hujiaba section, Ningqiang, Deng-4 Member, thrombolitic dolostone, inter-algal frame dissolved pores partially filled with bitumen, polarized light; (g) Hujiaba section, Ningqiang, Deng-4 Member, stromatolitic dolostone, intra-laminal dissolved pores and cavities partially filled with bitumen; (h) Hujiaba section, Ningqiang, Deng-4 Member, stromatolitic dolostone, intra-laminal dissolved pores (generated due to dissolution of clastics-rich laminae) partially filled with bitumen, polarized light; (i) Gucheng section, Wangcang, Deng-4 Member, crystalline powder-scale dolostone, intercrystalline dissolved pores of non-selective dissolution origin partially filled with bitumen and quartz, polarized light; (j) Gucheng section, Wangcang, Deng-4 Member, crystalline powder-scale dolostone, intercrystalline dissolved pores and dissolved cavities of non-selective dissolution origin partially filled with bitumen and quartz, polarized light; (k) Gucheng section, Wangcang, Deng-4 Member, crystalline powder-scale dolostone, dolomite intercrystalline dissolved pores, weak quartz dissolution; (l) Bashan section, Zhenba, Deng-4 Member, dolarenite, non-selective intergranular dissolved pores occasionally filled with bitumen, polarized light.